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  • Articles: DFG German National Licenses  (40)
  • 2015-2019
  • 1995-1999  (40)
  • 1960-1964
  • 1925-1929
  • 1830-1839
  • 1995  (40)
  • Chemistry  (40)
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  • Articles: DFG German National Licenses  (40)
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  • 2015-2019
  • 1995-1999  (40)
  • 1960-1964
  • 1925-1929
  • 1830-1839
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  • 1
    Electronic Resource
    Electronic Resource
    Solution behavior of α-chymotrypsin dissolved in nonpolar organic solvents via hydrophobic ion pairing (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 451-456 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dissolution of α-chymotrypsin in nonpolar organic solvents can be achieved using hydrophobic ion pairing, whereby the polar counterions are replaced by a stoichiometric number of detergent molecules. Using Aerosol OT[AOT, sodium bis(2-octyl)sulfosuccinate], it is possible to partition significant amounts of the enzyme into alkanes and chlorocarbons. Apparent solubility in isooctane is greater than 1 mg/mL (80 μM). Necessary conditions for achieving effective partitioning of α-chymotrypsin into these solvents are described. Using CD spectroscopy, it can be shown that the AOT-α-chymotrypsin (CMT) complex retains its native secondary and tertiary structure when dissolved in alkanes, and that the globular structure is stable to more than 100°C. In contrast, α-chymotrypsin unfolds at 54°C in aqueous solution. The relative solubility of the AOT-CMT complex in a variety of alkanes and chlorocarbons is also reported. The native structure of α-chymotrypsin is maintained in carbon tetrachloride, but not in methylene chloride or chloroform. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350504
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  • 2
    Electronic Resource
    Electronic Resource
    Geowissenschaften (1995)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 29 (1995), S. XVI 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19950290517
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  • 3
    Electronic Resource
    Electronic Resource
    Biosynthetic Production of [N2,1,3,7,9-15N]Guanosine and [1,3,7,9-15N]inosine and conversion into [N6,1,3,7,9-15N]adenosine for structure elucidation of RNA by heteronuclear NMR (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 421-439 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure was developed for the biosynthetic preparation of 15N-labelled guanosine and inosine through the action of a mutant Bacillus subtilis strain. Crude [N2,1,3,7,9-15N]guanosine and [1,3,7,9-15N]inosine were isolated from the culture filtrate by precipitation and anion-exchange chromatography (Scheme 1). No cell lysis and no enzymatic degradation was necessary. The per-isobutyrylated derivatives 1 and 2 were isolated from a complex mixture, purified by virtue of their different lipophilicity, and separated in three steps involving normal-and reversed-phase silica-gel chromatography. One litre of complex nutrient medium yielded 8.44 mmol of guanosine derivative and 2.84 mmol of inosine derivative with high average 15N enrichment (83.5 and 91.9 atom-%, resp.). [N6,1,3,7,9-15N]Adenosine (4) was obtained from 2′,3′,5′-tri-O-isobutyryl[1,3,7,9-15N]inosine (1) through the ammonolysis of its 1,2,4-triazolyl derivative with aqueous 15NH3 (Scheme 2).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780213
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  • 4
    Electronic Resource
    Electronic Resource
    1,1-Hydroborierung von Alkinen mit 6-Aza-nido-decaboranen (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 947-951 
    Details
    ISSN: 0009-2940
    Keywords: 6-Aza-nido-decaborane ; 9-(1-Alkenyl)-6-phenyl-6-aza-nido-decaborane ; 1,1-Hydroboration of alkynes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,1-Hydroboration of Alkynes with 6-Aza-nido-decaboranes[1]Alkynes AC≡CR′ (R′ = Me, Bu, tBu, SiMe3), that contain a mobile group A, like H or SiMe3, undergo hydroboration by 6-aza-nido-decaboranes RNB9H11 (1a-c, R = H, Ph, PhCH2) and 1,2-migration of the group A, to give the corresponding 9-(1-alkenyl)-6-aza-nido-decaboranes RNB9H10(CH=CR′A) (2a-h). Ethenes AHC=CH2 (A = SiMe3, SnBu3) are hydroborated by 1a, b as well to form products of the type RNB9H10(CH2CH2A) (3a-c). The alkyne Me3SiC=CH undergoes a hydroboration with 1b twice; the formation of (PhNB9H10)2CHCH2SiMe3 (4) proceeds by a 1,1- and a 1,2-hydroboration step, apparently. The crystal structure analysis of (PhCH2)NB9H10[CH=CMe(SiMe3)] (2e; space group Pl) reveals a (Z configuration of the ethene moiety.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280916
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  • 5
    Electronic Resource
    Electronic Resource
    Öffnung des Aza-closo-dodecaboran-Gerüsts durch Basen (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1225-1229 
    Details
    ISSN: 0009-2940
    Keywords: 1-Organo-1-aza-closo-dodecaborane(12) ; Trialkylamine-1-organo-1-aza-nido-dodecaborane(12) (1/1) ; Undecahydro-1-organo-1-aza-nido-dodecaborate(1-), 2-hydro-, 2-halogeno-, 2-alkoxy-, 2-amino-, 2-alkyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Opening of the Aza-clso-dodecaborane Skeleton by BasesThe aza-closo-borane PhNB11H11 (1a) is opened by the amines NR3 (R = Me, Et) to give the novel aza-nido-dodecaboranes PhNB11H11(NR3) (2a, b). The non-planar open pentagonal face of 2a, b accomodates the N atom, a BHB bridge, and the base-bound B atom, according to NMR spectra and the crystal structure analysis of monoclinic 2b. A similar but more symmetric structure is found when closo-RNB11H11 (1a-c, R = Ph, Me, H) is attacked by anionic bases X- to give nido-RNB11H11X- (3a-j; R/X = Me/H, Me/F, Me/Cl, Ph/OH, H/OMe, Me/OMe, Me/OtBu, Me/NEt2, Me/Me, Me/Bu). The anions are precipitated with cations [K([18]crown-6)], [S(NMe2)3], [N(PPh3)2], [Et2NH2], or [Li(tmeda)2]. The nido-structures of type 2 and 3 are derived from the hypothetical closo-NB12H13.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281214
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of polyimides endcapped with phenylethynylphthalic anhydride (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2141-2149 
    Details
    ISSN: 0887-624X
    Keywords: polyimides ; 4-phenylethynylphthalic anhydride ; thermooxidative stability ; high-temprature MAS NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of high glass transition temperature (Tg 〉 300°C), amorphous, soluble, poly-imide oligomers of controlled molecular weight endcapped with 4-phenylethynylphthalic anhydride endcapping agent is described. The 4-phenylethynylphthalic anhydride was employed to afford a higher curing temperature (380-420°C) which widens the processing window compared to unsubstituted acetylene-endcapped polyimides. The polyimides were synthesized via solution imidization techniques, using the ester-acid of various dianhydrides and aromatic diamines. A “ one-pot” procedure utilizing NMP as the solvent and o-dichlo-robenzene as the azeotroping agent reproducibly produced fully imidized, but yet soluble wholly aromatic polyimides. Thermally cured samples were prepared with gel contents of up to 98% that displayed good solvent resistance. Glass transition temperatures comparable to high molecular weight linear analogs were produced. These polyimides also show excellent thermal stability as judged by thermogravimetric analysis (TGA). Model phenylethynyl imide compounds were synthesized and used to follow and elucidate the nature of the products formed from the phenylethynyl curing by using high temperature magic-angle 13C nuclear magnetic resonance (MAS NMR). Preliminary results indicate that the cure reaction can be followed by MAS NMR. However, the nature of the products being formed during the curing process is difficult to determine by the solid-state MAS NMR alone. Differential scanning calorimetry (DSC) data clearly show that the model system does indeed melt and displays a wide window before the strong cure exotherm is observed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331307
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 219-228 
    Details
    ISSN: 0006-3592
    Keywords: formate conversion ; mass spectrometer ; anaerobic conversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H13CO3- pulses and measurement of 12CH4 and 13CH4 production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO2/CH4 production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high Ks value of 2.5 mmol m-3, it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO2 and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450306
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  • 8
    Electronic Resource
    Electronic Resource
    Glucose hydrolysis and oxidation in supercritical water (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 637-648 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose hydrolysis and oxidation occurred rapidly in supercritical water at 246 bar and at 425 to 600°C. A diverse set of products, present in the liquid-phase reactor effluent and also subject to hydrolysis, was formed. At 600°C and a 6-s reactor residence time, glucose is completely gasified, even in the absence of oxygen. In the presence of oxygen, destruction of liquid-phase products is enhanced, with none found above 550°C at a 6-s reactor residence time. Major products formed wee acetic acid, acetonylacetone, propenoic acid, and acetaldehyde in the liquid phase, and carbon monoxide, carbon dioxide, methane, ethane, ethylene, and hydrogen in the gas phase. Methane and hydrogen were present among the products at temperatures up to 600°C for reactor residence times of 6 s.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410320
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  • 9
    Electronic Resource
    Electronic Resource
    Acetic acid oxidation and hydrolysis in supercritical water (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2108-2121 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Acetic acid (CH3COOH) hydrolysis and oxidation in supercritical water were examined from 425 - 600°C and 246 bar at reactor residence times of 4.4 to 9.8 s. Over the range of conditions studied, acetic acid oxidation was globally 0.72 ± 0.15 order in acetic acid and 0.27 ± 0.15 order in oxygen to a 95% confidence level, with an activation energy of 168 ± 21 kJ/mol, a preexponential factor of 109.9 ± 1.7 and an induction time of about 1.5 s at 525°C. Isothermal kinetic measurements at 550°C over the range 160 to 263 bar indicated that pressure or density did not affect the rate of acetic acid oxidation as much as was previously observed in the oxidation of hydrogen or carbon monoxide in supercritical water. Major products of acetic acid oxidation in (upercriuical water are carbon dioxide, carbon monoxide, methaite, and hydrogen. Trace amounts of propenoic acid were occasionally detected. Hydrolysis or hydrothermolysis in the absence of oxygen resulted in approximately 35% conversion of acetic acid at 600°C, 246 bar, and 8-s reactor residence time. Regression of the limited hydrolysis runs assuming a reaction rate first-order in organic gave a global rate expression with a preexponential factor of 104.4 ± 1.1 and an activation energy of 94 ± 17 kJ/moL.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410910
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  • 10
    Electronic Resource
    Electronic Resource
    Accuracy in the chromatographic determination of extreme enantiomeric ratios: A critical reflection (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 567-571 
    Details
    ISSN: 0899-0042
    Keywords: enantiomer separation ; chromatographic resolution ; peak integration ; peak size ratio ; calibration curve ; determination of optical purity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic quantitation of very low amounts of an enantiomer in the presence of its antipode can be an extraordinary challenge. If resolution of the peaks is not complete even at extreme mass ratios an integrator will yield inaccurate results due to geometric effects. A given resolution can be adequate for peaks of similar size but result in severe overlap if one of the signals is markedly smaller. If tailing occurs, which is more the rule than the exception, the problem is especially severe for last eluted small peaks. Additional obstacles are detector nonlinearity and other sources of unsatisfactory calibration curves, overloading phenomena, and the possible lack of standards of highest optical purity. These problems have been studied by computer simulations and the liquid chromatographic separation of (R,S)-phenylethyl naphthoic acid amide on a chiral stationary phase. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070802
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